The present application claims priority upon Japanese Patent Application No. 2001-352176 filed Nov. 16, 2001, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to an ink-ejection-determining device determining whether or not ink has been ejected in a printing apparatus, an inkjet printer comprising an ink-ejection-determining device, a storage medium recording thereon a computer program that makes an ink-ejection-determining device execute ink-ejection determination, a computer system comprising the above-mentioned inkjet printer, and an ink-ejection-determining method.
2. Description of the Related Art
An inkjet printer prints images by ejecting ink from a plurality of nozzles provided in a print head. These nozzles may cause clogging due to increase in ink viscosity, mixture of bubbles, and other reasons. In this case, ink might not be ejected, and this may cause an unprinted section in an image (hereinafter, such a section will be referred to as xe2x80x9cdot-missxe2x80x9d), which may result in degradation in image quality.
In order to prevent the above-mentioned dot-missing, it is effective to clean the print head. However, if the print head is cleaned, some ink, although a slight amount, will be consumed, and there is a possibility that some kind of negative influence will be exerted on the nozzles that have no problem. In view of the above, there exist ink-ejection-determining devices that optically determine whether or not ink is being ejected in order to determine, before cleaning the print head, whether or not the nozzle is actually clogged, or to determine, after cleaning, whether or not ink is being normally ejected also through the nozzle that was clogged.
FIG. 11 shows a schematic view of an example of an ink-ejection-determining device using light. This determining device comprises a light emitter 302 that emits light, and a light receptor 304 that receives the light and outputs an output signal corresponding to the amount of light.
A laser diode forming a light source of the light emitter 302 will heat-up when it emits light; and this heat may cause a decrease in laser-beam intensity. Therefore, the light emitter 302 comprises: a monitor diode (not shown) which receives the laser-beam emitted from the laser diode at a position opposite from the light receptor 304 and detects an amount of light of the received laser beam; and a controller that controls the intensity of the laser beam according to the amount of light detected by the monitor diode. The light emitter 302 thus carries out a so-called automatic power control so that the intensity of the laser beam emitted from the laser diode will be constant.
The light receptor 304 comprises a light-receiving sensor 306. Between a gain-adjusting terminal Pa of the light-receiving sensor 306 and a supply voltage Vcc, there is connected a so-called gain resistor Rg; and an output signal Vout is output from a signal-outputting terminal Pb.
Determination of whether ink has been ejected or not is made according to a change in the output level of the output signal Vout caused by blocking of the laser beam by ink Ip ejected from a print head 300 of a printing apparatus. That is, it is set so that the output signal Vout of the light-receiving sensor 306 switches between an ON level and an OFF level according to whether or not the ink Ip blocks the laser beam. In order for the output of the light-receiving sensor 306 to certainly switch between the ON level and the OFF level according to whether the ink has been ejected, it is required that the amount of light received by the light-receiving sensor 306 is stable. After the light emitter 302 is turned on, the level of the output signal in the light-receiving sensor 306 in respect to the intensity of this laser beam is adjusted using the gain resistor Rg.
However, the temperature of the monitor diode, which is provided to control the intensity of the laser beam emitted by the laser diode, may also rise with the heating-up of the laser diode, and there is a possibility that the sensitivity of the monitor diode will change. Therefore, even if the output-signal level of the light-receiving sensor 306 is adjusted in respect to the intensity of the laser-beam from the light emitter 302 after the light emitter 302 is turned on, since the temperature of the monitor diode will rise with lapse of time, a change will occur in the intensity of the laser-beam which is supposed to be controlled according to the amount of light received by this monitor diode.
Therefore, a problem arises in that, even though the output signal of the light-receiving sensor 306 is adjusted after the light emitter 302 is turned on, since the laser beam intensity will be changed at the time of determining ink ejection, the output of the light-receiving sensor 306 will not change between the ON level and the OFF level even when the ink ejected from the print head blocks the laser-beam, and it will be erroneously determined that a nozzle is clogged.
The present invention has been contrived in view of the above and other problems, and an object thereof is to realize a highly-reliable ink-ejection-determining device capable of determining whether or not ink has been ejected, an inkjet printer comprising this ink-ejection-determining device, a storage medium recording thereon a computer program that makes an ink-ejection-determining device, execute ink-ejection determination, a computer system comprising the above-mentioned inkjet printer, and an ink-ejection-determining method making it possible to determine, with a high reliability, whether or not ink has been ejected.
A main invention is an ink-ejection-determining device comprising: a light emitter capable of emitting light; and a light receptor capable of receiving the light and outputting an output signal corresponding to an amount of the light; wherein: according to a change in the output signal caused by the light being blocked by ink ejected from an ink-ejecting portion, the ink-ejection-determining device makes a determination of whether or not ink has been ejected; and if it is determined, according to the change in the output signal, that ink has not been ejected, after conducting a correction of a gain of the light receptor according to the output signal of the light receptor, the correction being conducted to make the output signal of the light receptor suit the determination of ink ejection, the ink-ejection-determining device again makes the determination of whether or not ink has been ejected.
Another main invention is an ink-ejection-determining device comprising: a light emitter capable of emitting light; and a light receptor capable of receiving the light and outputting an output signal corresponding to an amount of the light; wherein: according to a change in the output signal caused by the light being blocked by ink ejected from an ink-ejecting portion, the ink-ejection-determining device makes a determination of whether or not ink has been ejected; and if it is determined, according to the change in the output signal, that ink has not been ejected, after conducting a correction of an intensity of the light emitted by the light emitter according to the output signal of the light receptor, the correction being conducted to make the output signal of the light receptor suit the determination of ink ejection, the ink-ejection-determining device again makes the determination of whether or not ink has been ejected.
Features and objects of the present invention other than the above will become clear by reading the description of the present specification with reference to the accompanying drawings.